ILLINOIS NATURAL HISTORY SURVEY MANUAL 1 



B. REPRODUCTIVE 



Plants that propagate by means of their vegetative parts, 

 such as by stolons as we have noted, have an asexual or vegetative 

 means of reproduction. Plants that grow anew from seed have a 

 sexual Wit^ns of reproduction through the functioning of special- 

 ized organs in the flower. 



Fig. 4. — The complete flower. I. — Pistil; a, ovary; b, style; 

 C, stigma. II. — Stamen; d, filament; e, anther, gross view; f, anther, 

 cross-section. III. — Perianth; g, sepal; h, petal. 



THE FLOWER 



The complete flower. — A complete flower, fig. 4, consists 

 of four kinds or sets of organs — pistils, stamens, petals and 

 sepals. There is a type of flower in which these parts are 

 spirally arranged around a central axis, but in all other flowers 

 each set of organs makes up its own circle around the center ot 

 the flower and is called a whorl. In many flowers the organs are 

 distinct and easily recognized; in others they are considerably 

 modified. 



Pistils. — ^The innermost whorl comprises one or more pistils . 

 A pistil, fig. 4 I, usually has three parts. The enlarged portion 

 at the base, a, is the ovary. Two or more individual pistils may 

 occur, fused together so as to make the whole structure appear 

 to be a single one having rounded projections, which mark the 

 true number of pistils present. This is the compound pistil^ and 



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